Hypocomplementemia may be used more generally to refer to decreased complement levels while secondary complement disorder is to low complement levels that are not directly due to a genetic cause but secondary to another medical condition.
These levels can be used to distinguish conditions:
- Systemic lupus erythematosus causes low C3 and C4
- Membranoproliferative glomerulonephritis causes low C3, but normal C4
Read more about this topic: Complement Deficiency